If you have experienced an allergic reaction after coloring your hair.

Increasing severity of allergic reactions every time you color your hair

Continued use of hair coloring products without realizing you are allergic to them or while suspecting or knowing you have mild allergic reactions can cause the symptoms to get worse. The areas around your eyes and your whole face may swell severely. In addition, reactions may not only develop at the areas that came into direct contact with the coloring mixture or the rinse water but also may spread over a wide area beyond these areas of contact. More serious immediate hypersensitivity reactions may also occur, such as generalized hives, difficulty breathing, and drops in blood pressure, which can be extremely dangerous. Persons who have ever experienced allergic reactions should never use hair coloring products.
Even if your reactions only include itching but are felt or intensify with every use, you may be allergic to hair coloring products. You should not color your hair in the future. In addition, you may experience severe reactions at the test area, so do not even perform a skin allergy test (patch test). If you have ever experienced an allergic reaction, we recommend you use hair dyes (cosmetics) such as hair manicures and non-oxidative hair dyes.

Cross-reactions due to hair coloring products

You may develop an allergic reaction even if it is your first time using a certain hair coloring product. In addition, some who develop allergic reactions after coloring their hair may be allergic to products that are completely different from hair coloring products. This may occur when the causative ingredient in an oxidative hair dye and other products causing the reaction have similar chemical structures, so that exposing to either ingredient causes an allergic reaction. This is called a cross-reaction.
Ingredients that cause cross-reactions with oxidative dyestuffs (such as p-Phenylenediamine) in oxidative hair dyes include local anesthetics (benzocaine, procaine), skin-lightening agents (hydroquinone), and dyestuffs used on clothing and leather.